1. Field
The present disclosure relates to a fuel cell.
2. Description of the Related Art
In general, a solid polymer electrolyte fuel cell includes a solid polymer electrolyte membrane, which is a polymer ion-exchange membrane. The fuel cell includes a membrane electrode assembly (MEA), in which an anode electrode is disposed on one surface of the solid polymer electrolyte membrane and a cathode electrode is disposed on the other surface of the solid polymer electrolyte membrane. The anode electrode and the cathode electrode each include a catalyst layer (electrode catalyst layer) and a gas diffusion layer (porous carbon).
The membrane electrode assembly and separators (bipolar plates) that sandwich the membrane electrode assembly constitute a power generation cell (unit fuel cell). A predetermined number of power generation cells are stacked and used, for example, as a vehicle fuel cell stack.
Typically, a fuel cell is structured as a so-called “internal manifold fuel cell” so that a fuel gas and an oxidant gas, each of which is a reactant gas, can be respectively supplied to anode electrodes and cathode electrodes of power generation cells that are stacked.
The internal manifold fuel cell includes reactant gas inlet manifolds (a fuel gas inlet manifold and an oxidant gas inlet manifold) and reactant gas outlet manifolds (a fuel gas outlet manifold and an oxidant gas outlet manifold), each extending in a stacking direction of the power generation cells. The reactant gas inlet manifolds and the reactant gas outlet manifolds are connected to reactant gas channels (a fuel gas channel and an oxidant gas channel), which supply the reactant gases along electrode surfaces. The reactant gas inlet manifolds are connected to the inlets of the reactant gas channels, and the reactant gas outlet manifolds are connected to the outlets of the reactant gas channels.
In such a fuel cell, the opening areas of the reactant gas inlet manifolds and the reactant gas outlet manifolds are comparatively small. Accordingly, in order to make the reactant gases to flow smoothly over the entirety of electrode reaction surfaces, it is necessary to form buffer portions, which function to disperse the reactant gases, in the vicinities of the reactant gas inlet manifolds and the reactant gas outlet manifolds.
For example, Japanese Unexamined Patent Application Publication No. 2012-164467 describes a fuel cell that is capable of uniformly and reliably supplying reactant gases from the reactant gas inlet manifolds to the entirety of the reactant gas channels through the buffer portions. In the fuel cell, a first buffer portion, which connects a first reactant gas manifold and a first reactant gas channel to each other, is formed on one surface of a separator. A second buffer portion, which connects a second reactant gas manifold and a second reactant gas channel to each other, is formed on the other surface of the separator.
The first buffer portion includes a first dedicated buffer region that is adjacent to the first reactant gas manifold, through which one of the reactant gases flows, and that restricts flow of the other reactant gas on the second buffer portion side. The second buffer portion includes a second dedicated buffer region that is adjacent to the second reactant gas manifold, through which the other reactant gas flows, and that restricts flow of the one of the reactant gases on the first buffer portion side.
The first buffer portion and the second buffer portion respectively have common buffer regions through which the one of the reactant gases and the other reactant gas flow. The depth of each of the first dedicated buffer region and the second dedicated buffer region is larger than that of a corresponding one of the common buffer regions.
It is described that, with such a structure, the reactant gases can be uniformly and reliably supplied to the entirety of the first reactant gas channel and the entirety of the second reactant gas channel from the first reactant gas manifold and the second reactant gas manifold through the first buffer portion and the second buffer portion, respectively.